1. Field of the Invention
The invention relates to an apparatus for the treatment of workpieces comprising a treatment chamber, a conveyor and a sealing arrangement.
2. Background Art
The industrial treatment of large numbers of workpieces, especially for surface treatment but also for drying workpieces, has long preferentially been performed with apparatuses which continuously or discontinuously guide the workpieces through a treatment zone with the aid of a conveyor, because such apparatuses have an elevated capacity and may readily be incorporated into a production line. The treatment zone is here located in a treatment chamber, which frequently takes the form of a booth, the walls and ceiling of which divide the external atmosphere from the internal atmosphere of the treatment chamber and in particular prevent any escape of the treatment medium and optionally heat from the treatment chamber. Hereafter and in the claims, the term xe2x80x9cwallsxe2x80x9d will be used for simplicity""s sake to denote not only the walls strictly speaking but also the ceiling.
The treatment medium may comprise a treatment liquid, as is the case for example when coating workpieces or in preparative processes for coating. The treatment medium may, however, in principle also comprise gases, vapours or liquid or powder mists, as are present in spray booths, for example.
A second function of the treatment chamber walls is to prevent dirt from entering the treatment zone from outside. Care is in particular taken to ensure that those components of the conveyor which may possibly release contaminants, in particular the drive components, are arranged outside the treatment chamber. In order to carry the workpieces, such conveyors must comprise a carrier arm which extends through one wall of the treatment chamber and on the inner end of which the workpieces are held. To this end, the treatment chamber wall must comprise a slot which extends along the conveyor""s path of motion and which is closed by a separate sealing arrangement. This sealing arrangement is designed such that it opens locally in the area of the carrier arm.
In known apparatuses of the above-stated type, resilient sealing lips are used as the sealing arrangements, but such lips are not always reliable.
DE 198 48 946 C2 describes a different treatment apparatus of this type. In this latter apparatus, the sealing arrangement comprises a plurality of segmented sealing elements arranged adjacent to one another which overlap in the lateral direction and are pivoted about swivel pins to permit passage of the carrier arm. Such swivel pins are, however, not always desired.
The object of the present invention is accordingly to develop an apparatus of the above-stated type in such a manner that the slot between the two wall portions is reliably sealed, the sealing arrangement nevertheless operating reliably while requiring little maintenance.
Said object is achieved by an apparatus for the treatment of workpieces comprising a treatment chamber, a conveyor, a sealing arrangement, and a first and second deflecting device. The treatment chamber comprises at least one wall and comprises the treatment zone for the workpieces. The conveyor, which guides the workpieces through the treatment chamber, further comprises: at least one conveyor element outside the treatment chamber; and at least one carrier arm, which extends through a slot, extending along the conveyor""s path of motion, in the at least one wall of the treatment chamber. The sealing arrangement seals the slot in the at least one wall of the treatment chamber. The sealing arrangement is capable of being opened in each case locally in the vicinity of the carrier arm to allow passage of the carrier arm. Further the sealing arrangement comprises a plurality of mobile sealing elements.
Additionally, the sealing arrangement further comprises a first set of springs, which overlap laterally and are attached in an area remote from the slot to a portion lying on one side of the slot of the at least one wall of the treatment chamber and a second set of spring strips, which overlap laterally and are attached in an area remote from the slot to a portion lying on the other side of the slot of the at least one wall of the treatment chamber. In their resting position, the mutually facing end zones of the spring strips belonging to the first set and of the spring strips belonging to the second set overlap resiliently.
The first deflecting device is provided which is movable by the conveyor together with the carrier arm and, when moved, engages beneath the first set of spring strips and bends them out resiliently in such a manner that the carrier arm can pass through the first set of spring strips. Similarly, the second deflecting device is provided which is movable by the conveyor together with the carrier arm and, when moved, bends out the second set of spring strips resiliently in such a manner that the carrier arm can pass through the second set of spring strips.
Thus, according to the invention, no parts which move as a whole are used as the sealing element. Opening of the sealing arrangement is based solely on resilient flexing of the spring strips. The deflecting devices are designed such that, when they are moved together with the carrier arm, they bend the upper and lower spring strips apart in the manner of a plough, so permitting passage of the carrier arm. The spring strips subsequently automatically return to their sealing resting position. In the event that workpiece treatment involves exposure to liquid, the inclination of the spring strips belonging to the two sets may in each case be selected and maintained such that any sprayed liquid which impinges on the spring strips flows back into the interior of the treatment chamber.
The spring strips preferably consist of spring steel, stainless steel or an optionally reinforced plastic.
Preferably, a shield is provided, which is movable together with the carrier arm and covers that zone of the sealing arrangement in which the spring strips are bent out of their resting position. This shield thus provides additional protection from treatment medium, in particular treatment liquid, escaping from the area of the sealing arrangement which is opened locally in the vicinity of the carrier arm.
The deflecting devices are preferably strips of sheet metal which are bent in such a manner that their surface extends everywhere approximately parallel to the areas of the spring strips lying thereagainst. In this manner, the deflecting devices have a guidance action which causes little wear and generates little noise.
It is furthermore convenient for the deflecting devices to be guided such that they lie against the spring strips everywhere at approximately the same distance from the edges thereof. The distance between that point on the spring strips at which the deflecting devices engage and the edge of the spring strips at which they are attached thus remains approximately constant everywhere.
A particularly preferred embodiment of the invention is one in which the slot between the first portion and the second portion of the wall of the treatment chamber is additionally closed on the outside by a bellows and a deflector is provided, which is movable with the carrier arm and comprises at least one sloping face, against which one edge of the bellows rests locally and which displaces the edge of the bellows in such a manner that the carrier arm can pass through the bellows.
The bellows are preferably used where a maximally good, even gas-proof, separation is desired between the external atmosphere and the internal atmosphere of the treatment chamber. The bellows is still more capable than the sealing arrangement consisting of spring strips of preventing the escape of vapours, mists and condensates; gas leakage losses can be kept so low that it is possible to maintain a different pressure within the treatment chamber than in the external atmosphere or in the zone between the spring strips and the bellows.
Finally, it is particularly convenient if the deflecting devices are configured symmetrically with regard to a plane perpendicular to the direction of conveying in such a manner that they are effective in both the forwards and backwards direction of the conveying motion.
The treatment chamber may, for example, be a booth in which the workpieces are surface treated, in particular coated, wherein the wall in which the slot is located is a substantially vertical wall of the booth.
In this case, it may be particularly favourable if the spring strips belonging to the different sets are bent out in different directions by the deflecting devices.
The treatment chamber may, however, also in particular be the chamber of a dryer or oven, wherein the wall in which the slot is located is the ceiling of the dryer or oven chamber. In this case, the primary function of the sealing arrangement is to insulate the dryer or oven chamber thermally and to prevent the escape of the hot internal atmosphere and the penetration of cold ambient air.
In this case, it is frequently favourable if the spring strips belonging to the different sets are bent out in the same direction by the deflecting devices.